Dynamic effects related to steady-state multiplicity in continuous Saccharomyces cerevisiae cultivations |
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Authors: | Lei Frede Olsson Lisbeth Jørgensen Sten Bay |
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Institution: | CAPEC, Department of Chemical Engineering, Building 227, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark. |
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Abstract: | The behavioral differences between chemostat and productostat cultivation of aerobic glucose-limited Saccharomyces cerevisiae were investigated. Three types of experiments were conducted: a chemostat, where the dilution rate was shifted up or down in stepwise manner; and a productostat, with either stepwise changed or a rampwise increased ethanol setpoint, i.e., an accelero-productostat. The transient responses from chemostat and productostat experiments were interpreted using a simple metabolic flux model. In a productostat it was possible to obtain oxido-reductive steady states at dilution rates far below Dcrit due to a strong repression of the respiratory system. However, these steady states could not be obtained in a chemostat, since a dilution rate shift-down from an oxido-reductive steady state led to a derepression of the respiratory system. It can therefore be concluded that the range of dilution rates where steady-state multiplicity can be obtained differs depending on the operation mode and that this dilution rate multiplicity range may appear larger in a productostat than in a chemostat. A more narrow multiplicity range, however, was obtained when the productostat was operated as an accelero-productostat. |
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Keywords: | Saccharomyces cerevisiae productostat respiration steady‐state multiplicity dynamics |
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